Chapter Objectives

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Chapter Objectives

• In this chapter, you will learn
• About operating systems and their key functions
• How system resources help hardware and software
  communicate
• About the steps in the boot process
• How to use Device Manager and System Information
  to examine the system

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Introducing Operating Systems

• An operating system (OS) is software that
  contains instructions that coordinate all the
  activities among computer hardware resources

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Operating System Components

• Every operating system has two main internal
  components
• A shell is the portion of the OS that relates to
  the user and to applications
• The kernel is the part that loads when you first
  turn on your computer
• The Windows operating system uses a database
  called the registry to store hardware and
  software configuration information, user
  preferences, and application settings that are
  used when the OS is first loaded
• Some data is kept in text files called
  initialization files

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Operating System Components
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Types of Operating Systems

• DOS (Disk Operating System)
• Windows
• Unix
• Linux
• OS/2
• Mac OS

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An OS Provides a User Interface

• With a command-line interface, you type commands
  or press specific keys to enter data and commands
  to instruct the OS to perform operations
• A menu-driven interface provides menus as a way
  to enter data and commands
• With a graphical user interface (GUI), you issue
  commands by selecting icons, buttons, windows, or
  other graphical objects on the screen

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An OS Manages Files and Folders
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An OS Manages Applications

• Installing and Loading Application Software

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An OS Manages Applications

• Handling Multiple Programs
• Single tasking vs. Multitasking
• For an operating system to support multitasking,
  the CPU must be running in protected mode
• In protected mode, the CPU processes 32 bits of
  data at one time
• In real mode, the CPU processes 16 bits of data
  at one time
• With preemptive multitasking, the operating
  system allots CPU time to an application for a
  specified period, and then preempts the
  processing to give the CPU to another application

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An OS Manages Hardware
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How an OS Uses Device Drivers
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How an OS Uses Device Drivers

• Installing a device in a system that supports
  Plug and Play usually is a simple process
• With Plug and Play (PnP), if you connect a device
  to your computer, the operating system recognizes
  that hardware has been changed since the last
  time the computer was started or while the
  computer was running
• PnP is not entirely foolproof
• Manufacturers often update device drivers to
  address bugs or provide additional features

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How an OS Uses System BIOS to Manage Devices
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System Resources

• A system resource is a tool used by either
  hardware or software to communicate its
  requirements
• There are four types of system resources
• Interrupt requests (IRQs)
• Memory addresses
• I/O addresses
• Direct Memory Access (DMA) channels

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System Resources
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System Resources

• All four system resources depend on certain lines
  on a bus on the motherboard

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Interrupt Requests (IRQs)

• When a hardware device needs the CPU to do
  something, it uses a hardware interrupt
• The device initiates a hardware interrupt by
  placing voltage on the designated interrupt
  request (IRQ) line assigned to it
• On motherboards, part of the chip set called the
  interrupt controller manages the IRQs for the CPU
• Only 8 IRQs were supported by the interrupt
  controller on early motherboards. A second
  interrupt controller was later added, which
  communicates with the CPU through the first
  interrupt controller, and handles an additional 8
  IRQs
• Polling software constantly runs and has the CPU
  periodically check a hardware device to see if it
  needs service

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Interrupt Requests (IRQs)
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Interrupt Requests (IRQs)
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Memory Addresses

• An operating system relates to a memory location
  by using a memory address, a number that always
  uses 0 as its first digit

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I/O Addresses

• I/O addresses, also called port addresses or just
  ports, are numbers the CPU can use to access
  hardware devices
• The address bus on the motherboard carries memory
  addresses and I/O addresses
• If the address bus has been set to carry I/O
  addresses, then each device listens to this bus.
  If the address belongs to it, then it responds.
  Otherwise it ignores the request for information

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I/O Addresses
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I/O Addresses
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DMA Channels

• A direct memory access (DMA) channel lets an I/O
  device send data directly to memory, bypassing
  the CPU
• A chip on the motherboard contains the DMA logic
  and manages the process

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Booting Up Your Computer

• The process of starting or restarting a computer
  and loading the operating system is referred to
  as the boot process or booting
• When you turn on a computer that is powered off
  completely, you are performing a cold boot, or
  hard boot
• A warm boot, or soft boot, is the process of
  restarting a computer that already is powered on
• Uses the operating system to reboot
• A cold boot is slower and more stressful on your
  machine

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Startup BIOS Controls the Beginning of the Boot

• The functions performed during the boot can be
  divided into four parts
• Startup BIOS runs a process called the power-on
  self test and assigns system resources
• The ROM BIOS startup program searches for and
  loads an OS
• The OS configures the system and completes its
  own loading
• Application software is loaded and executed

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Startup BIOS Controls the Beginning of the Boot
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POST and Assignment of System Resources
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How the BIOS Finds and Loads the OS

• Once POST and the first pass at assignment of
  resources are complete, the next step is to load
  an OS
• Startup BIOS looks to CMOS setup to find out
  which device is set to be the boot device

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How the BIOS Finds and Loads the OS
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Loading the Core of Windows XP
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Loading the Core of Windows XP

• Files needed to boot Windows XP, Windows 2000, or
  Windows NT successfully

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Troubleshooting the Boot Process

• A successful boot depends on the hardware, the
  BIOS, and the operating system all performing
  without errors
• If a system will not boot, you may need to try to
  boot the computer from a floppy disk
• A floppy disk with enough software to load an
  operating system is called a boot disk, or
  recovery disk
• A boot disk with some utility programs to
  troubleshoot a failed hard drive is called a
  rescue disk, emergency startup disk (ESD), or
  startup disk
• It is important to have a rescue disk available
  in case of emergency
• These can be created in the operating sytem

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Operating System Tools to Examine a System
Device Manager

• Using Windows XP, Windows 2000, and Windows 9x,
  Device Manager is the primary tool used to manage
  hardware devices
• The Device Manager will also show how the IRQs
  are assigned on your computer
• If a device is problematic, you can use Device
  Manager to review the properties for that device,
  or update the driver

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Operating System Tools to Examine a System
Device Manager
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Operating System Tools to Examine a System
System Information

• The System Information utility provides more
  detailed information than that provided by Device
  Manager
• The System Information utility lists
• The BIOS version
• The directory where the OS is installed
• How system resources are used
• Information about drivers and their current
  status
• The System Information utility allows you to save
  or print a report listing system information

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Operating System Tools to Examine a System
System Information
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Chapter Summary

• In this chapter, you learned
• About operating systems and their key functions
• How system resources help hardware and software
  communicate
• About the steps in the boot process
• How to use Device Manager and System Information
  to examine the system

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• Chapter 2 Complete